As compared with a conventional mechanical key, a capacitive key does not need any mechanical contact, and as compared with a conventional metallic touch key, it is able for the capacitive key to prevent the potential risk due to the direct contact of a human body with a metallic sheet and to eliminate the application limitations. The capacitive key is durable and convenient to use (e.g., it may be controlled by lightly touching it), and has a well appearance. In addition, in combination with signal processing operations, it is very easy to quantize and adjust key switches. Currently, the capacitive key has been widely applied to such electrical appliances as mobile phones, televisions, washing machines and refrigerators.
However, in the related art, a specific induction capacitance detection chip and an associated external circuit need to be used, so as to achieve the capacitive touch operation. Usually, the induction capacitance detection chip includes a plurality of integrated multi-point detection chips. This specific integrated induction capacitance detection chip must also be used even in the case that an induction capacitance for a single contact point is to be detected, resulting in a waste of resources and a high detection cost.